fixed error in post_pop_up and altereted search bar placeholder text

frontend/src/components/home/job_postings/post_pop_up.js

@@ -36,6 +36,8 @@ export default function PostPopUp({ post }) {
     const findKeyWords = () => {
         let job_description = post.job_description;
 
+        if (!post.job_highlights.Qualifications) return;
+
         for (const keyphrase of post.job_highlights.Qualifications) {
             const start = job_description.indexOf(keyphrase);
             const end = start + keyphrase.length;

frontend/src/components/home/job_postings/search_bar.js

@@ -11,7 +11,7 @@ const SearchBar = (props) => {
         <form className="search-job" onSubmit={handleSubmit}>
             <input 
                 type="text" 
-                placeholder="Search by title, company or any jobs keyword..."
+                placeholder="Search for a job (ex. software developer in chicago or marketing manager in new york via linkedin)"
                 value={props.query}
                 onChange={(e) => props.setQuery(e.target.value)}
                 required